The invention relates to a method and apparatus for determining which of a plurality of originals to be copied bear images of a sharpness which warrants copying, particularly to a method and apparatus of such type making use of photoelectric scanning.
Commonly owned U.S. patent application Ser. No. 395,366 of Volker Weinert et al., filed Sept. 7, 1973, discloses a method of the type in question. With that method, the transparency values of adjoining portions of the original to be copied are measured, and the difference determined. A plurality of such differences are determined, and from the sum of such differences conclusions are drawn concerning the contrast in the image borne by the original to be copied. However, the performance of that method requires the use of at least two light detectors for forming the difference signals. This necessarily results in a relatively high cost for the matching of the two light measuring circuits to each other and does not particularly facilitate the measurement.